Conveyors comprising endless conveyor belts have long been used for transporting parcels, articles or objects. Conveyors are used for moving objects, such as parcels or parts, through a sorting facility, a manufacturing plant or an assembly plant for example.
There is often a need to transport articles from a first conveyor to a second conveyor, where the first and second conveyors are not longitudinally extending from one another. For example, it is not uncommon for two straight conveyor runs of a conveying system to be perpendicularly oriented to each other, such as where, due to building size and/or space constraints, the conveyor sections cannot extend fully longitudinally. Specialized curved conveyor sections are used to connect the output end of the first conveyor section to the input end of the second conveyor section. Curved conveyors known in the prior an have angular paths extending between offsets of only a few degrees to curved conveyors extending through a 180 degree angular path.
Conveyor turns are usually powered so that the material moves through the curved conveyor section from the first or input conveyor to the second or output conveyor section. Power to cause the curved conveyor belt to rotate is coupled to the belt through a variety of means. Powered end rollers are commonly used to cause the belt to rotate. Or the belt can be pinched at a belt edge between a rotating capstan and pinch roller. Other conveyor belts for powered belt turns may be driven at the center of the conveyor belt.
There are numerous patents relating to powered belt turns in conveyor systems. For example, in U.S. Pat. No. 3,951,256, issued to Gurewitz, an endless, arcuate shaped conveyor belt carries articles around curves in a conveyor system. The arcuate conveyor belt is supported for rotation between two end rollers and a bed supports the conveyor belt in a horizontal plane. One of the end rollers is chain driven by a motor located beneath the belt turn, thus causing the belt to rotate about the end rollers. Another powered belt turn is set forth in U.S. Pat. No. 3,044,603 issued to Fry. In Fry, a frusto-conically shaped conveyor belt is mounted for rotation between end rollers. The conveyor belt is powered by a shaft driven end roller in a manner similar to the Gurewitz device. Still another patent showing a powered belt turn is Russian patent No. 575,082. In the Russian patent, a cone shaped conveyor belt is supported for rotation by a fixture at the center of the conveyor belt. The cone shaped belt is also supported by angularly displaced tension rollers and is driven to provide a powered belt turn.
When tapered rollers are used at the ends of the belt turn where the belt reverses direction, the moving belt tends to creep down the taper. The prior art powered belt turns discussed above describe different means for maintaining the conveyor belt on the end rollers. In Gurewitz, roller guides, which are attached to an inside surface of the conveyor belt, ride in an arcuate, grooved member that is mounted between upper and lower belt runs. In Fry however, the conveyor belt is maintained in position on the end rollers by a chain extending peripherally about the belt edge and a tongue assembly which attaches the chain to the outer periphery of the conveyor belt. The chain is guided by an angled guide fabricated of low friction material. In the Russian patent, the cone shaped belt is supported in contact with angularly displaced tension rollers by the fixture. The cone shaped belt is shown clamped to the fixture by a cone shaped plug and bolt assembly; thus, the cone shaped belt is not moveable axially with respect to the tension rollers.
Another approach for maintaining the curved belt in position on the conveyor turn known in the prior art, includes applying a bead to the outer periphery of a frusto-conically shaped conveyor belt. The conveyor belt's outer periphery is then positioned within a roller guide assembly that extends adjacent the outer conveyor belt periphery and captures the bead between cooperating pairs of rollers. Depending on the size of the belt turn, there could be a hundred or more cooperating pairs of rollers necessary to maintain the conveyor belt in position as it turns.
These prior an devices for maintaining the conveyor belt in position on a powered belt turn tend to be mechanically complicated, noisy and expensive. They also require high maintenance and have been found to wear rapidly, requiring frequent adjustment and replacement. The curved conveyor belts also tend to be difficult to adjust or replace. When adjustment becomes necessary, the belt turns of the prior art must often be shut down while making the adjustments. When a belt is damaged to such an extent that replacement is required, substantial machine disassembly is necessary to be able to remove and replace the damaged belt. Thus, a typical consequence of having to replace a belt is considerable machine down-time.
Therefore, it would be desirable to have a powered belt turn that has an inexpensive and mechanically simple means for maintaining the curved conveyor belt in position on the belt turn. Furthermore, there is a need for a powered belt turn that can be operated at high belt speeds and high belt loading. There is also a need for a powered belt turn which allows the curved belt to be easily changed without significant machine disassembly or machine down-time.